In a statement issued today a spokesperson for Barclays said: “Barclays works closely with its regulators in all jurisdictions and will continue to cooperate with the New York Attorney General. However, we do not believe that this suit is justified, and we have a duty to our shareholders, clients and staff to defend our position.”

In June New York attorney general Eric Schneiderman, claimed that the UK lender dramatically increased its market share of its dark pool by falsifying statements to clients and investors about how its operates.

In a statement, released at the time, the attorney general said that contrary to Barclays’ claims that it had put in place special safeguards to protect clients from “aggressive” or predatory high-frequency traders, its dark pool operation favoured high-frequency traders.

Dark pools are trading systems where dealing can be conducted without traders having to reveal their identity and prices are kept private.